This invention generally relates to medical instruments such as retrieval devices for retrieving material from within a body. More particularly, the invention relates to retrieval devices for capturing and releasing stones such as urinary tract stones, gall stones, and other biological materials.
Medical retrieval devices generally are used to retrieve biological and foreign material from the body including stones. Such medical retrieval devices may be used through an endoscope or a laparoscope.
One type of known device has a sheath and a retrieval assembly such as a basket that is movable in and out of the sheath. When the basket is within the sheath, the basket assumes a collapsed, reduced diameter profile. When the sheath is retracted relative to the basket or the basket is moved beyond the end of the sheath, the basket expands to a relatively larger diameter than when the basket is enclosed within the sheath. Generally, the contour of known baskets is round or oval and is formed by a plurality of legs.
With many known retrieval devices, it is technically difficult to release captured material such as a stone from the retrieval assembly once the stone is captured. In some patients, for example, a cicatrix or some other constriction that reduces the diameter of the lumen of the tract may form in the tract in which the stone is lodged because of recurrent trauma caused by the stone to the lining of the tract. The narrowed lumen of the tract may not be so narrow so as to interfere with insertion of a retrieval device while the retrieval device is in a collapsed position. However, after the retrieval device is inserted into the tract, the retrieval assembly expanded, and the stone captured within the device, the diameter of the retrieval assembly containing the stone may exceed the inner diameter of the narrowed lumen of the tract or the inner diameter of the orifice of the tract into which the retrieval device is inserted. If an excessive pulling force is used by the operator in an attempt to remove the retrieval device and stone, the retrieval device may traumatize the orifice or the lining of the tract or, worse, perforate the tract. In addition, the retrieval device may assume an everted configuration causing damage upon being withdrawn from the tract. Under these conditions, the stone must first be released from the retrieval device followed by withdrawal of the collapsed retrieval device from the tract. If the stone can not be released from the retrieval device, more invasive, surgical approaches are required to disengage the stone from the retrieval device and to remove the retrieval device from the body tract.
With most, if not all, current medical retrieval device designs, it is difficult to disengage the stone or other material from the retrieval assembly so that the retrieval device can be collapsed and then removed from the body. Although existing medical instruments are capable of delivering laser energy or chemicals to fragment the stone, these devices are sometimes difficult to position in the body while the retrieval device holding the stone is still in the body.
It is an object of the invention to provide a medical instrument, i.e., a medical retrieval device with features that permit the device to open to an open position for capturing biological material and to an elongated, expanded open position for releasing captured material. The invention thus involves a device and related method for capturing material in the body such as a stone and then releasing the captured material from the retrieval device while the retrieval device is still positioned in the body. The material can be biological or foreign material such as stones or any of a variety of other types of material within a body. The material can be located in a urinary or biliary tract in the body or elsewhere in the body.
A medical instrument according to the invention is used to treat an internal organ which includes material such as a calculus or a thromboembulus. The medical instrument typically includes a handle, a sheath, and a retrieval assembly such as a basket. An elongated member may extend within the sheath along an axis from a proximal end to a distal end of the sheath. The elongated member and sheath are sized for insertion into a body. The handle is located at the proximal end of the elongated member and the sheath.
The retrieval assembly of the medical retrieval device has at least a proximal portion and a distal portion. The distal portion is used to capture material in a body when the distal portion extends from the distal end of the sheath and while the proximal portion is collapsed within the sheath. The retrieval assembly expands to release captured material when the distal and proximal portions of the retrieval assembly extend from the distal end of the sheath. The contour of each portion of the retrieval assembly may be similar to or different from the other portions of the retrieval assembly.
In one embodiment, the retrieval assembly is a basket. The basket has a plurality of legs, for example, the basket has four legs or the basket has three sets of paired, helical legs. The basket legs can be preformed and the baskets can be atraumatic. Atraumatic baskets have a zero-tip or tipless configuration, and/or may have legs that are D-shaped, B-shaped, V-shaped, or half-round in cross-section such that the legs of the basket are atraumatic.
In an alternate embodiment, the retrieval assembly has a plurality of loops, for example, two opposing loops. The loops of the retrieval assembly are joined at a base of the retrieval assembly. The distal ends of the loops of the retrieval assembly are not joined at the distal end of the retrieval assembly.
In one embodiment of the medical retrieval device of the invention, the proximal portion of the retrieval assembly is generally straight; the contour of the proximal portion being planar rather than curved. Alternatively, at least the proximal portion of the retrieval assembly is bulbous, i.e., the proximal portion is bowed out from the center of the retrieval device when the proximal portion is deployed beyond the distal end of the sheath. Other features of the retrieval assembly can include paired spiral basket legs. The legs of the basket can be, for example, round, oval or half-round. The legs may be preformed.
The invention contemplates any number of portions to the retrieval assembly and is not limited to a proximal and distal portion. For example, the retrieval assembly may have a proximal, intermediate and distal portion.
Other embodiments of this invention include a sheath axially moveable relative to the retrieval assembly. In this embodiment, retraction of the sheath in a direction away from the distal end of the sheath extends the retrieval assembly from the distal end of the sheath. One or more portions of the retrieval assembly are thereby expanded depending on which portions are uncovered by the retracted sheath. Thus, the outer dimensions of the retrieval assembly are adjustable as the retrieval assembly is moved relative to the sheath.
Another embodiment of the invention includes an elongated guide member longitudinally positioned in the lumen of the sheath, operably attached to a proximal end of the retrieval assembly and actuated by at least one actuating member on the handle. Reciprocal axial movement of the elongated guide member moves the retrieval assembly from its enclosed position within the sheath, in and out of the distal end of the sheath and back to its enclosed position within the sheath. As the assembly is moved in and out the sheath, the portions of the retrieval assembly shift between collapsed and opened positions.
In yet another embodiment, the sheath includes a plurality of compressible, generally longitudinal slits for retraction of the sheath. In an alternate embodiment, the sheath includes a plurality of slots, each slot having a slideably movable retractor pin operably attached to the sheath to retract the sheath. In yet another embodiment, retraction of the sheath is accomplished by rotating the sheath on a threaded mechanism. Each of these embodiments of the sheath, i.e., longitudinal slits, slot and pin, and rotatable sheath, allow the operator to make continuous adjustments to the size of the retrieval assembly as it is moved in and out of the sheath.
In yet another aspect, the invention relates to a method for retrieving material from a body. The method comprises inserting a medical retrieval device with a retrieval assembly (such as the instrument described above) into a body, extending the distal portion of the retrieval assembly beyond the end of the sheath, maneuvering the retrieval assembly around the material while the distal portion of the retrieval assembly is extended beyond the distal end of the sheath, capturing the material within the retrieval assembly, withdrawing the proximal and distal portions of the retrieval assembly back into the sheath, and removing the medical instrument and the material captured in the retrieval assembly from the body.
Alternatively, following capture of the material in the distal portion of the retrieval assembly, the proximal portion of the retrieval assembly is extended, the material released from the proximal portion, the proximal and distal portions of the retrieval assembly are withdrawn into the sheath and the medical instrument removed from the body.
In yet another aspect, the invention relates to a method for end-encapsulation or side encapsulation of materials from within a body. The method comprises inserting the medical instrument having a retrieval assembly with loops (such as the device described above) into a body while the loop retrieval assembly is completely enclosed within the sheath. When the material, such as a stone, is approached, the distal portion of the retrieval assembly is extended beyond the distal end of the sheath. If a larger basket is required, the proximal portion of the retrieval assembly may also be extended beyond the distal end of the sheath. While the loops of the distal portion of the retrieval assembly are parted, the retrieval assembly is advanced directly over the stone located at the distal end of the retrieval assembly. The stone is end-encapsulated by advancing the distal end of the retrieval assembly directly over the stone so that the stone enters the retrieval assembly through the opening created by the parted loops of the distal portion of the retrieval assembly. Thus, the loop retrieval assembly can easily xe2x80x9cpluckxe2x80x9d stones from embedded regions such as the calyces of the kidney. Alternatively, the loop retrieval assembly may capture a stone through or between the loops at the side of the retrieval assembly. The captured material can be released from the loop retrieval assembly by extending the proximal portion of the loop assembly beyond the distal end of the sheath. When the proximal portion as well as the distal portion of the loop assembly is extended beyond the distal end of the sheath, a stone encapsulated within the retrieval assembly can be released from the retrieval assembly or between the parted ends of the loops at the distal end of the retrieval assembly or between or through the loops at the side of the retrieval assembly. If the captured material is not to be released, the sheath is advanced relative to the retrieval assembly causing the assembly loops to grip the captured material. The medical instrument is removed from the body.